Regelsbrunner Aue

Regelsbrunner Aue

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Key features of the case study

Restore hydrological connectivity and ecological integrity between the river and its floodplains in a segment of the Austrian Danube

Attention: The information presented below has been taken from Tockner et al.(1999)

Site description

The study was conducted in the free-flowing section of the Danube River about 25 km downstream of Vienna (river-km 1895 and 1909). The area designated for restoration is a 570-ha floodplain sector on the right orographical bank of the Danube River (‘Regelsbrunner Aue’). At mean water level, the channel network is 37 km long, corresponding to a floodplain channel density of 6.5 km km² and a total surface area of all floodplain water bodies of 120 ha. The backwater system is dominated by a former river channel (total length, ca. 10 km) that was cut off from the main river channel at its upstream end more than 100 years ago. This main side channel is subdivided by weirs into semi-isolated water bodies (channel segments I–IX in Figure 1). At present, this side channel has surface water connections to the river at its downstream end for about 180 days annually. Long stagnant periods are interrupted by short-term flood pulses (average duration, B4 days) caused by upstream connections at high water levels via former inflow areas in the streamside embankments. However, the floodplain system is dynamically connected to the river via its porous aquifer (seepage inflow). Water levels in the floodplain system follow the water level fluctuations of the Danube after only a short time lag.</p>

Ecological response

The biotic ‘functional describers’ include macrophytes, molluscs, odonates, amphibians, fish and benthic invertebrates. In the present analysis, the first four of these groups are focused upon, because sampling strategies for fish and benthic invertebrates are not compatible with the other groups.

Related Measures

• Add/feed sediment
• Establish environmental flows / naturalise flow regimes
• Favour morphogenic flows
• Remove barrier
• Manage sluice and weir operation for fish migration
• Initiate natural channel dynamics to promote natural regeneration
• Remove or modify in-channel hydraulic structures
• Reconnect backwaters and wetlands
• Remove hard engineering structures that impede lateral connectivity

Related Pressures

• Artificial barriers upstream from the site
• Artificial barriers downstream from the site
• Channelisation / cross section alteration
• Embankments, levees or dikes
• Sedimentation and sediment input